Answer:

Step-by-step explanation:
Given

Required
Determine the roots
To get the root of the function, then f(b) must be 0;
i.e. f(b) = 0
So, the expression becomes

Add 75 to both sides


Take square roots of both sides


Reorder

Expand 75 as a product of 25 and 3

Split the expression




The options are not clear enough; however the roots of the equation are 
4x + 7x - 2 + 5x - 10 = 180
16x - 12 = 180
16x = 192
x = 12
m<A= 4x = 4(12) = 48
m<B = 7x - 2 = 7(12) - 2 = 84 - 2 = 82
m<C = 5x - 10 = 5(12) - 10 = 60 - 10 = 50
X-7=13
move -7 to the right side of the equation, change the sign from negative to positive when you move it
x-7+7=13+7
x=13+7
x=20